liballoc: mark str.to_owned() and String::from(&str) as #[inline].

Fixes #53681

Prepare miri engine for enforcing validity invariant during execution

In particular, make recursive checking of references optional, and add a `const_mode` parameter that says whether `usize` is allowed to contain a pointer. Also refactor validation a bit to be type-driven at the "leafs" (primitive types), and separately validate scalar layout to catch `NonNull` violations (which it did not properly validate before).

Fixes https://github.com/rust-lang/rust/issues/53826
Also fixes https://github.com/rust-lang/rust/issues/54751

r? @oli-obk

also less verbose logging

Also, make enum variant handling a bit nicer

We'll try ruling out undef later

Fixes #54751

This does not actually regress anything.  It would regress NonNull, but we
didn't handle that correctly previously either.

user annotations in patterns

Fixes https://github.com/rust-lang/rust/issues/54573

r? @pnkfelix

[NLL]  Improve closure region bound errors

Previously, we would report free region errors that originate from closure with the span of the closure and a "closure body requires ..." message. This is now updated to use a reason and span from inside the closure.

structured suggestions for unused-lifetimes lint

Regretfully, resolve_lifetime.rs is suffering from a bit of rightward-drift, but

![zero_life](https://user-images.githubusercontent.com/1076988/46253407-010e7880-c430-11e8-8faf-b9afc1405415.png)

r? @nikomatsakis

Remove unnecessary comma in `libstd/thread/mod.rs` doc comment

Fix typo in `libstd/thread/mod.rs` doc comment: remove unnecessary comma.

Backport 1.29.2 release notes to master

r? @ghost

Cleanup: remove graphviz::IntoCow

It's just `Into<Cow<...>>` and the applicable methods already exist for `Vec`/`[T]` and `String`/`str`.

Clarify docs for when binary_search has many matches.

Fixes https://github.com/rust-lang/rust/issues/51817.

Thanks to reviewers Tyler Mandry (for pointing out that this is
ridiculous and we need a helper function), Niko Matsakis (for pointing
out that the span-calculation code only has a couple free variables),
and Esteban Küber (for pointing out `get_generics`).

Add the library search box on the 404 page

It actually has a link to search already, but it would be better to
have the search "box" as like index.md to be consistent.

<style> can be shared with index.md, but these pages currently
use https://doc.rust-lang.org/rust.css directly.

Fixes #14572.

Add doc for impl From for Error

As part of issue #51430 (cc @skade).

The impl is very simple, let me know if we need to go into any details.

Fix dead code lint for functions using impl Trait

Fixes https://github.com/rust-lang/rust/issues/54754

This is a minimal fix that doesn't add any new queries or touches unnecessary code. Please nominate for beta backport if wanted.